The present invention relates to a flame retardant resin composition adopting a non-halogen based flame retardant agent. In more detail, it relates to a flame retardant resin composition excellent in flame retardancy, mechanical properties, wet heat resistance and electric properties and suitable for mechanical parts, electric and electronic parts, automobile parts, housings and other parts of office automation apparatuses, household electric appliances, etc.
Thermoplastic resins such as polyester resins, polyamide resins and ABS resins are being used as injection molded materials in a wide range of fields such as mechanical parts, electric and electronic parts, automobile parts, office automation apparatuses and household electric appliances because of their excellent properties. On the other hand, these thermoplastic resins are inherently combustible, and when they are used as industrial materials, they are often required to be safe against flames, i.e., flame retardant, in addition to being well balanced in physical properties. Especially as for flame retardancy, in recent years, since moldings are reduced in weight and size, hence also in thickness, thin moldings are required to be highly flame retardant.
Thermoplastic resins are generally made flame retardant by compounding a halogen based organic compound as a flame retardant agent and an antimony compound as a flame retardation assistant into the resin. However, this method tends to evolve a large amount of smoke at the time of burning.
So in recent years, it has been strongly desired to use a flame retarding agent free from any halogen based compound.
For making a thermoplastic resin flame retardant without using any halogen based flame retardant agent, it is widely known to add a hydrated metal compound such as aluminum hydroxide or magnesium hydroxide, but to achieve satisfactory flame retardancy, the hydrated metal compound must be added in such a large amount as to degrade the properties peculiar to the resin disadvantageously.
On the other hand, as a method for making a combustible resin flame retardant without using such a hydrated metal compound, the use of red phosphorus is disclosed in Japanese Patent Laid-Open (Kokai) Nos. 60-168758, 61-219706, 63-89567, 1-129061, 2-169666, 3-197553, 6-9887, 6-145504, 6-263983, etc. However, though these patent gazettes disclose a flame retarding method of adding red phosphorus to a combustible resin, for example, adding red phosphorus to PET, they do not describe at all about the use of PET and/or (co)PET for making a combustible resin flame retardant, the use of PET/(co)PET/red phosphorus as a flame retardant agent of a combustible resin, or a combination of a liquid crystal polyester with a specific structure and red phosphorus. Furthermore, though the resin compositions obtained by these methods show excellent flame retardancy when the moldings obtained from them are thick (1/16"), they are not sufficient in flame retardancy disadvantageously when the moldings obtained from them are thin (1/32"), contrary to the demand in recent years for resins. Furthermore, these resin compositions have such problems that they are lowered in mechanical properties because of the flame retardant agent contained, and that the flame retardant agent bleeds out during dry heat or wet heat treatment, to contaminate the electric contacts of connectors.